Solubility product constants for natural dolomite (0–200 °C) through a groundwater-based approach using the USGS produced water database

The calculation of a reliable temperature dependent dolomite solubility product constant (Ksp?dol) has been the subject much research over last 70 years. This study evaluates log10(aCa2+/aMg2+) values using PHREEQC (Pitzer approach) for screened subset (n = 11,480) formation waters in U.S. Geological Survey National Produced Waters Geochemical Database V2 (PWGD), an extensive inventory 165,960 formational from range sedimentary lithologies North America up to 6.6 km depth (Blondes and others, 2016). Through ground truthing against datasets sourced Texas Gulf Coast basin Mississippi Salt Dome we establish both geochemical data PWGD new geothermal model US that is used determine temperatures at-formation-depth be sources. vast majority (90%) samples have log10(aCa2+/aMg2+)-temperature are interpreted indicative calcite-dolomite equilibrium buffering by bulk mineral solubilities. Using statistical models with different parameterisations (different Maier-Kelly formulas, mixed-effects various random effects linear models) regressed estimated Ksp?dol between 0 200 °C. process relies on well constrained calcite (Ksp?cal). Local modify evaluated through addition mixed which improves reliability enables determination local phases. nature these open interpretation, but suggest primary influence stoichiometry phase systematically modifying values. We discount order, solution ionic strength, equilibration anhydrite chlorite group minerals, illitization smectite albitization feldspar. For equation; (model J23) chosen as most representative yields pKsp?dol (log10Ksp?dol); pKsp°?dol ?17.27 ± 0.35 (25 °C, 1 atm) close prior estimates, including recent experimental value reported Bénézeth 2018 (pKsp°?dol ?17.19 0.3) validating groundwater regression analysis approach this study.